Be Ready for Questions About Molnupiravir to Treat COVID-19

You'll hear buzz about molnupiravir, an oral antiviral to treat COVID-19...now that it's under Health Canada review.

Molnupiravir blocks viral replication by incorporating itself into the RNA of SARS-CoV-2...causing viral death.

It's 4 capsules bid for 5 days...and seems well tolerated.

Evidence suggests molnupiravir may prevent hospitalization in about 1 in 35 unvaccinated outpatients age 18 or older with mild to moderate COVID-19...who are at high risk of developing severe illness.

This seems similar to injectable COVID-19 monoclonal antibodies, or "MAbs," (bamlanivimab, etc)...but there aren't direct comparisons.

Consider molnupiravir's downsides. For example, there's a concern it may lead to more viral variants...since it incorporates into viral RNA.

Plus animal studies suggest molnupiravir may cause birth defects. Anticipate that it will NOT be authorized for pregnant patients.

Expect eligibility criteria for molnupiravir to be similar to MAbs.

This will likely include adults with a positive COVID-19 test who are at high risk of severe illness (advanced age, chronic kidney disease, diabetes, etc)...regardless of vaccination status.

But patients should start molnupiravir within 5 days of symptoms...versus 10 days with MAbs.

Don't expect widespread use of molnupiravir right away...until there's more evidence. And especially avoid molnupiravir for patients under age 18, in pregnancy, or for postexposure prophylaxis.

Don't suggest combining molnupiravir with a MAb...due to lack of data.

Reinforce that treated patients still need to self-isolate. There's no evidence that molnupiravir or MAbs prevent spread of infection.

Emphasize COVID-19 vaccination...treatment is not a substitute. Patients on molnupiravir can be vaccinated as soon as they stop isolation.

Stay tuned for the antiviral Paxlovid (nirmatrelvir/ritonavir). It may overshadow molnupiravir...partly because it seems more effective.

Dig deeper into the evidence for these oral antivirals and COVID-19 MAbs in our chart, Treatments of Interest for COVID-19.


Key References

  • N Engl J Med. 2021 Dec 16. doi: 10.1056/NEJMoa2116044
  • https://www.canada.ca/en/public-services-procurement/news/2021/12/government-of-canada-signs-agreements-for-covid-19-oral-antiviral-treatments.html (12-23-21)
  • https://covid.cadth.ca/covid-news/ (12-23-21)
  • https://www.fda.gov/media/154418/download (12-23-21)
  • https://www.fda.gov/media/154419/download (12-23-21)
Pharmacist's Letter Canada. January 2022, No. 380101



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